Certain patients exhibit a need for cardiac or neural stimulation. This stimulation can be achieved by using an implantable medical device. When such a need exists, cardiac tissue can receive cardiac electrostimulation. Such stimulation can evoke a resulting heart contraction, and can be used to maintain a rate of heart contractions that will meet a patient's metabolic need for cardiac output, or to spatially coordinate heart contractions so as to improve the heart's pumping efficiency. Similarly, non-cardiac neural tissue can receive neural stimulation, e.g., neurostimulation energy. Neurostimulation may be used to affect the autonomic balance between the sympathetic nervous system (which tends to speed up certain metabolic processes) and the parasympathetic nervous system (which tends to slow down certain metabolic processes). Some patients may benefit from both cardiac and neural stimulation.
In order to effectively meet the needs of patients requiring cardiac and/or neural stimulation, implantable medical device manufacturers have developed a variety of implantable medical devices. Cardiac rhythm management devices are one type of implantable medical device that monitor the heart, provide therapy to the heart, or both, and can incorporate cardiac or neural stimulation, or both. Typically the cardiac stimulation is provided through one or more leads configured specifically for cardiac stimulation. Neural stimulation is also typically delivered through one or more leads configured specifically for neural stimulation. In addition to leads configured for cardiac or neural stimulation, an implantable medical device can also include various sensors for sensing a variety of physiological parameters that can assist in delivering proper therapy to the patient.
Many modern implantable medical devices are capable of communicating with local or remote devices located outside of the body. These external devices can be used to receive information from the implantable medical device including sensor information and information about events, such as when the implantable medical device has provided therapy (also referred to as the device response). In some cases, the external communication or interface device can also transmit operational parameters to the implantable medical device, or in other words program the implantable medical device. An example external communication device is the LATITUDE® patient management system. Implantable medical devices, such as cardiac rhythm management devices, can be programmed with a number of different parameter settings that affect the manner in which therapy is delivered. Combined therapy devices include programmable parameters for each type of therapy that can be delivered by the device.